Answer:
Some of the demerits or disadvantages of using a very slow castings rates in production of metal by the method of casting includes, with the solidification of metal, it may begin even before the mold is filled fully, which may result in defects such as shrinkage.
Secondly, the rate of slow casting will create castings that have a grain coarse structure that will affect the strength of the castings.
Step-by-step explanation:
Solution
The disadvantageous of slow casting rates in the production of metals by casting method is explained below:
(1) The solidification of metal may start even before the mold is filled completely, which may create or produce defects such as mis-runs and shrinkage and shrinkage cavity.
So, the slow cavity rate will produce partial and incomplete castings
(2) Slow casting rate will produce castings which have a coarse grain structure which therefore affects the strength of the castings adversely.